The invention relates to a disc brake, in particular for a commercial vehicle, and to a brake pad for a disc brake.
To brake a vehicle, brake pads are pressed with their friction linings against a brake disc on both sides by means of a pneumatically or electromotively driven brake application device, frictional heat arising due to conversion of the kinetic energy and resulting in considerable heating of the brake disc.
This introduction of heat causes radial expansion of the brake disc which is usually of a ring shaped design.
In conventional brake discs with a tubular or conical neck portion, however, this expansion is obstructed, and because of this the brake disc is deformed reversibly in a way also likened to an “umbrella”.
High thermal load, in conjunction with a suppressed radial expansion of the brake disc, may lead to high mechanical compressive stresses with the overshooting of the material yield strength. Upon cooling and when the stresses are reduced, overshooting of the tensile strength of the material may then occur, thus giving rise to surface cracks which are propagated ever further.
On the other hand, the “umbrella” action results in an uneven contact pattern of the brake pads, along with a concentration in the introduction of heat and local overheating of the brake disc.
In order to prevent this, solutions have already been proposed in which a structural separation of the friction ring of the brake disc from the brake disc neck allows uniform expansion, as a result of which not such high stresses occur in the material and the brake disc remains flat. However, these solutions can be implemented only with considerable outlay in manufacturing terms.
Optimization of the introduction of heat, particularly in order to prevent local overheating of the brake disc, is achieved by way of an elastic isobar brake pad, as it is known, which, however, necessitates a highly complicated and space consuming brake pad concept and, moreover, is also suitable only for low brake application forces, such as occur in the case of railroad brakes.
The object on which the invention is based is to develop further a disc brake and a brake pad of the generic type, such that the functional reliability of the disc brake is improved and the service life both of the brake disc and of the brake pads is prolonged.
This and other objects are achieved by a disc brake, in particular for a commercial vehicle, with a brake caliper that engages over a brake disc and in which brake pads capable of being pressed against the brake disc via at least one brake application device and having, in each case, a lining carrier plate and a friction lining fastened thereon, are positioned on both sides of the brake disc. The brake application device has at least one brake piston engaging on the lining carrier plate on the end face. At least one of the brake pads is mounted in an articulated manner, preferably tiltably, in a radial direction of the brake disc. The objects are achieved as well by a corresponding pad having a lining carrier plate with a friction lining fastened thereon, wherein the lining carrier plate has at least one recess with a curved base.
The invention makes it possible to have a thermally induced radial expansion of the brake disc, so that the effects described above when this expansion is obstructed cannot occur. The mounting of the brake pads corresponds in its action to the part lining brake discs mentioned, but, in contrast to these, in terms of its load bearing capacity, that is to say the ability to transmit brake application forces, is unchanged, as compared with the brake pads conventionally used in commercial vehicles.
In addition to more uniform heat and pressure distribution during the umbrella action of the brake disc, with an optimal design oblique radial wear of the brake disc and brake pads, such as has occurred hitherto, can also be reduced.
It should be emphasized especially that the invention can be implemented at a low outlay in structural and manufacturing terms, that is to say, is basically cost neutral.
Against this, there are the substantially longer service life of the brake disc and a gain in terms of functional reliability. This is due, above all, to the fact that the formation of cracks in the brake disc or brake disc ring is avoided and there is no need for a premature exchange of the brake disc.
In this context, mention may also be made of the increased operating reliability of the disc brake overall, which arises, in particular, from the fact that the hitherto existing risk of destruction of the brake disc, sometimes even of the entire disc brake, occurring as a result of the formation of cracks during the operation of the disc brake is prevented.
Whereas, in a fixed caliper disc brake, both brake pads are pressed onto the brake disc by two brake application devices equipped in each case with at least one brake piston, a sliding caliper disc brake functions according to the reaction principle. In this case, first, an application side brake pad is pressed by the brake application device onto the brake disc which then forms an abutment for the sliding caliper which, at the same time driving the opposite reaction side brake pad, is pushed opposite to the first application direction, until the reaction side brake pad comes to bear frictionally on the brake disc.
In this case, according to the invention, the reaction side lining carrier plate is mounted in an articulated manner, preferably tiltably, on the rear wall of the brake caliper, for which purpose the wall of the brake caliper and the lining carrier plate facing said wall are configured correspondingly.
For this purpose, according to an advantageous development of the invention, an elevation curved convexly in cross section is integrally formed onto the lining carrier plate or the wall of the brake caliper and matches with a recess, adapted to the contour of the projection, of the opposite part supported thereon. In this case, the elevation extends virtually in the form of a strip in the longitudinal direction of the brake pad transversely to the axis of the brake disc.
Instead of a strip, the lining carrier plate or the wall of the brake caliper may be provided with a plurality of crowned protuberances which engage into spherical cap shaped recesses of the opposite side which are adapted thereto.
Such a design is appropriate in the press on region of the brake piston on the application side lining carrier plate, the brake piston being composed of an adjusting spindle held rotatably in a bridge and of a thrust piece, which is held fixedly in terms of rotation on the lining carrier plate and is connected rotatably to the adjusting spindle and of which the free end face bearing against the lining carrier plate either is shaped as a crowned protuberance or has the spherical cap shaped receptacle.
It is also contemplated, however, to tie the thrust piece to the adjusting spindle in an articulated manner in such a way that a tilting movement in the radial direction of the brake disc is possible. In this case, the contact surfaces of the thrust piece and of the lining carrier plate may be planar or have another contour.
The elevation or recess may also be provided, instead of directly on or in the lining carrier plate, in a separate thrust plate bearing against the latter.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.